JP2020176845A - Geological structure evaluation method, geological structure evaluation system, and geological structure evaluation program - Google Patents

Abstract

To provide a geological structure evaluation method, a geological structure evaluation system, and a geological structure evaluation program which can further adequately evaluate a geological structure of natural ground.SOLUTION: An evaluation device 20 comprises a control unit 21, an elastic wave velocity distribution map storage unit 22 in which an elastic wave velocity distribution map is stored, and a geological structure information storage unit 23. The control unit 21 specifies object areas in a two-dimensional sectional view generated from a three-dimensional velocity distribution map stored in the elastic wave velocity distribution map storage unit 22. With respect to each object area of the specified object areas, the control unit 21 specifies low-velocity parts and uses spacings and shapes of velocity contours around the low-velocity parts to specify extension directions of valley parts extending from the low-velocity parts. If it is determined by using the extension directions of the valley parts that a plurality of low-velocity parts are consecutive, the control unit 21 specifies them as a soft part in the object area and stores a position (coordinates) of this soft part in the geological structure information storage unit 23.SELECTED DRAWING: Figure 1

Description

The present invention relates to a geological structure evaluation method, a geological structure evaluation system, and a geological structure evaluation program for evaluating the geological structure of a geological structure using an elastic wave velocity distribution map.

Conventionally, seismic reflection exploration is known as a method for grasping the geology of the ground in front of the tunnel face. In this exploration method, elastic waves are generated in a tunnel, and the reflected waves reflected at geological boundary surfaces (reflecting surfaces) having different physical properties are measured to identify the position of the reflecting surface. Then, the reflecting surface is determined to be some kind of discontinuous surface (geological boundary or fault) existing in the ground.

Therefore, a technique for evaluating the geological structure of the ground in front of the tunnel face is disclosed by using the position of the reflecting surface in the planned excavation area of the tunnel (see, for example, Patent Document 1 and Non-Patent Document 1). In the technique described in Patent Document 1, the reflected wave reflected in the ground is extracted from the observation waveform of the seismograph, and the reflected intensity distribution in the ground is created by using these reflected wave data and the reference elastic wave velocity. Then, this reflection intensity distribution is divided into a heterogeneous zone in which points having a large reflection intensity are densely distributed and a homogeneous zone in which the points with a large reflection intensity are not densely distributed, the reflection intensity at these boundaries is calculated, and each calculated based on this reflection intensity. Correct the position of each boundary on the tunnel axis using the modified elastic wave velocity in the zone.

Non-Patent Document 1 describes a tunnel face front spacecraft for exploring a geological discontinuity zone (crush zone, aquifer, etc.) in front of the tunnel face. In the measurement of this spacecraft, elastic waves are generated by blasting a small amount of explosive in the oscillation hole installed in the hole wall in the tunnel mine. Then, the reflected wave reflected from the geological discontinuity zone in front of the face is received and recorded by a plurality of three-component receivers installed in the hole wall in the mine. After that, the acquired reflection waveform is analyzed, and an elastic wave velocity distribution map in front of the face including the reflection surface in the ground (mainly the boundary surface of the stratum whose velocity and density change) is output.

Japanese Unexamined Patent Publication No. 2016-95140

FTS Co., Ltd. "Product information: Forward exploration" Tunnel face forward probe "TSP303", [online], [Search on March 18, 2019], Internet <URL: http://www.fts-web.jp / products /? id = 1449404839-259243 & mca = 5 & ca = & sk =>

Since reflected waves are generated on surfaces with distinctly different geological properties, it has been difficult to accurately detect configurations and soft parts where geological boundaries are repeated over a short range in seismic reflection surveys. Further, it is usually determined that the low speed portion is a soft portion. However, since the position of the low velocity portion in the elastic wave velocity distribution map output by the probe of Non-Patent Document 1 does not always match the position of the low velocity portion estimated from the reflecting surface, this elastic wave velocity The reliability of the position of the low-velocity part of the distribution map was low, and the geological structure could not be evaluated accurately.

The geological structure evaluation method for solving the above problems is a geological structure evaluation method for evaluating a geological structure using an elastic wave velocity distribution map, in which a low velocity portion is specified in an elastic wave velocity distribution map in a target area, and the low velocity portion is specified. Using the spacing and shape of the velocity contours around the velocity section, the extension direction of the valley extending from the low velocity section is specified, and the extension direction of the valley is used to continuously connect a plurality of low velocity regions. If it is determined to be present, it is specified as a soft portion in the target area.

According to the present invention, the geological structure of the ground can be accurately evaluated.

The schematic block diagram explaining the structure of the geological structure evaluation system in embodiment. The explanatory view of the hardware configuration in an embodiment. The flow chart explaining the processing procedure of the geological structure evaluation processing in an embodiment. Explanatory drawing explaining the three-dimensional elastic wave velocity distribution diagram in embodiment. It is explanatory drawing explaining the 2D velocity distribution sectional view in embodiment, (a) shows 2D vertical sectional view, and (b) shows 2D horizontal sectional view. It is explanatory drawing explaining the processing for each target area in an embodiment, (a) is a state which specified the low speed part, (b) is a state which specified the extension direction of a valley part, (c) is a continuous low. The state in which the velocity region is determined, (d) indicates the state in which the position of the soft portion is specified. It is explanatory drawing explaining the position of a soft part in an embodiment, (a) shows a two-dimensional vertical sectional view, (b) shows a two-dimensional horizontal sectional view. A two-dimensional horizontal sectional view for explaining a modified example.

Hereinafter, an embodiment in which the geological structure evaluation method, the geological structure evaluation system, and the geological structure evaluation program are embodied will be described with reference to FIGS. 1 to 7.
As shown in FIG. 1, in the present embodiment, the evaluation device 20 as the geological structure evaluation system is used.

(Hardware configuration)
The hardware configuration of the information processing apparatus H10 constituting the evaluation apparatus 20 will be described with reference to FIG. The information processing device H10 includes a communication device H11, a storage unit H14, and a processor H15. This hardware configuration is an example, and can be realized by other hardware.

The communication device H11 is an interface that establishes a communication path with another device and executes data transmission / reception, such as a network interface card or a wireless interface. The storage unit H14 is a storage device that stores data and various programs for executing various functions of the evaluation device 20. An example of the storage unit H14 is a ROM, RAM, hard disk, or the like.

The processor H15 controls each process in the evaluation device 20 by using the programs and data stored in the storage unit H14. Examples of the processor H15 include a CPU, an MPU, and the like. The processor H15 expands a program stored in a ROM or the like into a RAM and executes various processes for each service.

The processor H15 is not limited to one that performs software processing for all the processing executed by itself. For example, the processor H15 may include a dedicated hardware circuit (for example, an integrated circuit for a specific application: ASIC) that performs hardware processing for at least a part of the processing executed by the processor H15. That is, the processor H15 is (1) one or more processors that operate according to a computer program (software), (2) one or more dedicated hardware circuits that execute at least a part of various processes, or ( 3) It can be configured as a circuitry including a combination thereof. The processor includes a CPU and a memory such as a RAM and a ROM, and the memory stores a program code or a command configured to cause the CPU to execute a process. Memory or computer-readable media includes any available medium accessible by a general purpose or dedicated computer.

(System configuration)
Next, the function of the evaluation device 20 will be described with reference to FIG.
The evaluation device 20 is a computer system that evaluates the geological structure. An input device 15 and a display device 16 are connected to the evaluation device 20. The input device 15 is a keyboard, a pointing device, or the like, and is used for inputting various information. The display device 16 is a display or the like that displays various information. In this embodiment, a three-dimensional elastic wave velocity distribution map, a two-dimensional velocity distribution cross-sectional view, a position of a soft portion, and the like are displayed.

The input device 15 acquires a three-dimensional elastic wave (P wave) velocity distribution map from the measuring device 10 and supplies it to the evaluation device 20. In the present embodiment, the tunnel face forward spacecraft "TSP303" manufactured by "Amberg Technology" is used as the measuring device 10.

The measuring device 10 receives and records the reflected wave generated in the hole wall in the tunnel mine and reflected in the geological discontinuity zone in front of the face by a plurality of three-component receivers installed in the mine. Then, the measuring device 10 analyzes the acquired reflection waveform, calculates the elastic wave velocity in each of the three-dimensional grids (coordinates) constituting the evaluation target region, generates a three-dimensional elastic wave velocity distribution map, and stores it. To do. Further, the measuring device 10 includes the position (coordinates) of the reflecting surface in front of the tunnel face in the elastic wave velocity distribution map.

The evaluation device 20 includes a control unit 21, an elastic wave velocity distribution map storage unit 22, and a geological structure information storage unit 23.
The control unit 21 executes the evaluation process of the geological structure. The control unit 21 performs a process described later (a process including a cross-sectional view creating step, an area specifying step, a soft portion specifying step, and the like). By executing the geological structure evaluation program for this purpose, the control unit 21 functions as a cross-sectional view creation unit 211, an area identification unit 212, and a soft unit identification unit 213.

The cross-sectional view creating unit 211 executes a process of generating a two-dimensional cross-sectional view from the three-dimensional elastic wave velocity distribution map. In the present embodiment, it is assumed that the sectional view creating unit 211 generates a horizontal sectional view and a vertical sectional view orthogonal to the horizontal sectional view. Here, the horizontal cross-sectional view and the vertical cross-sectional view are cross-sectional views in which the central axis thereof is the central axis of the tunnel and the front of the tunnel face.

The area specifying unit 212 executes a process of dividing into a target area in the two-dimensional sectional view. In the present embodiment, the target area including the number of speed contours smaller than the maximum number of contours is divided. In this case, the area specifying unit 212 divides the target area with a portion where the speed change is gradual (a region where the density of the speed contour is low) as a boundary. Therefore, the area specifying unit 212 stores the maximum number of contours and the reference contour density for specifying the divided surface in which the speed change is gradual. The reference contour density is calculated from the number of contours included in the area of a predetermined distance (for example, several meters) in the tunnel excavation direction.

The soft portion specifying unit 213 executes a process of specifying the position (coordinates) of the soft portion in each target area. The soft portion specifying portion 213 specifies the position of the soft portion by specifying the range of the low speed region by using the speed contour. The soft portion specifying unit 213 records data on a continuous condition for determining that a plurality of low speed regions are continuous in order to specify the range of the low speed region. This continuous condition includes the distance from the end of the adjacent valley (proximity distance) and the allowable range of deviation in the extension direction of both valleys (connection angle range). Then, the soft portion specifying unit 213 identifies a portion connecting neighboring valley portions satisfying the continuous condition as a soft portion, and records the portion in the geological structure information storage unit 23.

The elastic wave velocity distribution map storage unit 22 stores the three-dimensional elastic wave velocity distribution map acquired from the measuring device 10. This three-dimensional elastic wave velocity distribution map is stored when it is acquired from the measuring device 10. In this elastic wave velocity distribution map, elastic wave velocities are recorded in each grid (three-dimensional coordinates) constituting the evaluation target region. The grid of the present embodiment is arranged at each position divided into 1000 equal parts in the traveling direction of the tunnel and 200 equal parts in the vertical and horizontal directions. Further, the elastic wave velocity distribution map includes the position (coordinates) of the reflecting surface specified by the measuring device 10.

FIG. 4 is a specific example of a three-dimensional elastic wave velocity distribution map stored in the elastic wave velocity distribution map storage unit 22. The grid around FIG. 4 shows a predetermined length (for example, 10 m width) in the elastic wave velocity distribution map.

The geological structure information storage unit 23 stores the geological structure information in which the position of the soft portion is specified by the evaluation device 20. This geological structure information is stored when the geological structure evaluation process described later is executed. In the present embodiment, the position of the soft portion (coordinates in the two-dimensional cross section) in the two-dimensional velocity distribution cross-sectional view in the horizontal direction and the vertical direction is stored as the geological structure information.

(Geological structure evaluation process)
Next, the geological structure evaluation process will be described with reference to FIGS. 3 to 7.
First, the control unit 21 of the evaluation device 20 executes the acquisition process of the three-dimensional elastic wave velocity distribution map (step S1-1). Specifically, the cross-sectional view creation unit 211 of the control unit 21 acquires a three-dimensional elastic wave velocity distribution map from the elastic wave velocity distribution map storage unit 22.

Next, the control unit 21 of the evaluation device 20 executes a process of creating a two-dimensional velocity distribution cross-sectional view (step S1-2). Specifically, the cross-sectional view creation unit 211 of the control unit 21 specifies the tunnel 30 and the planned excavation area 31 in front of the face in the three-dimensional elastic wave velocity distribution map. Then, the cross-sectional view creating unit 211 cuts out a vertical cross-sectional view and a horizontal cross-sectional view on the vertical plane and the horizontal plane including the planned excavation area 31.

As shown in FIG. 4, a vertical sectional view VP1 in which the velocity contour included in the vertical plane is extracted and a horizontal sectional view HP1 in which the velocity contour included in the horizontal plane is extracted are cut out from the three-dimensional elastic wave velocity distribution map. In the figure, the curve in each cross-sectional view (VP1, HP1) shows the velocity contour. Further, the shaded area is the reflection surface RS1 specified by the measuring device 10.

FIG. 5A is a two-dimensional velocity distribution cross-sectional view (vertical cross-sectional view VP1) on the cut-out vertical plane, and FIG. 5B is a two-dimensional velocity distribution cross-sectional view (horizontal cross-sectional view HP1) on the cut-out horizontal plane. ). At the center of the vertical sectional view VP1 and the horizontal sectional view HP1, the area of the tunnel 30 and the planned excavation area 31 beyond the face surface 30f are located. In addition, in FIGS. 5A and 5B, the planned excavation area 31 is shown as a hatching area.

Next, the control unit 21 of the evaluation device 20 executes the division process of the target area (step S1-3). Specifically, the area specifying unit 212 of the control unit 21 calculates the contour density for each unit distance, compares it with the reference contour density, and specifies a plurality of division candidate positions whose contour density is equal to or less than the reference contour density. .. Further, the area specifying unit 212 calculates the number of contours included in this distance according to the distance from the division start position to the specified division candidate position, and compares it with the maximum number of contours.

Then, the area specifying unit 212 specifies the division candidate position in which the calculated number of contours is equal to or less than the maximum number of contours as the division end position. The area specifying unit 212 is divided as one target area from the division start position at the division end position. Next, the area specifying unit 212 divides the next target area by repeating the calculation of the contour density and the number of contours and the specification of the division end position again with the division end position of the target area as the division start position. This process is repeated for the entire planned excavation area.

Then, the following processing is repeated for each of the divided target areas.
In the following processing, the area A1 shown in FIG. 5A will be described as one divided target area.

First, the control unit 21 of the evaluation device 20 executes the identification process of the low speed unit (step S1-4). Specifically, the soft portion specifying unit 213 of the control unit 21 identifies a closed figure whose elastic wave velocity is the lowest in the target area than its surroundings.
For example, in FIG. 6A, in the region A1, a closed figure (low velocity portion LS1) having a minimum velocity of elastic waves is specified.

Next, the control unit 21 of the evaluation device 20 executes a process of specifying the extension direction of the valley portion from the low speed portion (step S1-5). Specifically, the soft portion specifying portion 213 of the control unit 21 identifies a portion (protruding portion) having a shape having a small curvature on the outer circumference of the low speed portion LS1. Next, the soft portion specifying portion 213 specifies a constant velocity region composed of the next velocity contour around the low velocity portion LS1, and uses the interval between the velocity contours and the curvature of the constant velocity region to obtain this velocity. Identify the protrusion on the contour. By repeating the identification of the protruding portion and connecting the specified protruding portions, the extension direction of the valley portion is specified. The identification of the valley portion ends at the position where the speed tendency is reversed in the speed contour.

In FIG. 6B, arrows indicate the direction in which the speed increases in the valley portion (extension direction of the valley portion) from the four low speed portions LS1. Here, in the valley portion extending from the low speed portion LS1, the portion where there is no speed contour indicating further speed increase or no protruding portion is the end portion.

Next, the control unit 21 of the evaluation device 20 executes a determination process of whether or not there is a continuous low-speed region (step S1-6). Specifically, the soft portion specifying unit 213 of the control unit 21 determines whether or not there is an end portion of another valley portion satisfying the continuous condition at the end portion of each specified valley portion. Here, the soft portion specifying portion 213 determines whether or not the distance between the ends of both valley portions is within the close distance. When the distance between the ends of both valleys is within a close distance, the soft portion specifying portion 213 is displaced in the extension direction of the valley at the ends of both valleys, or the end of the valley from the low speed portion. It is determined whether or not the deviation in the average extension direction up to is within the allowable range. Then, the soft portion specifying portion 213 determines that the continuous condition is satisfied when the deviation in the extension direction is within the allowable range.

In the portion C1 surrounded by a circle in FIG. 6 (c), since the continuous condition is satisfied, it is determined that the low speed region including the two valleys is continuous. Further, since the continuous condition is not satisfied in the portion marked with x, it is determined that the low speed region including the two valleys is not continuous.

Here, when it is determined that there is a continuous low speed region (when “YES” in step S1-6), the control unit 21 of the evaluation device 20 records that the continuous low speed region is a soft portion. The process is executed (step S1-7). Specifically, the soft portion specifying portion 213 of the control unit 21 generates a smooth line in which a low velocity region including two valley portions is connected in the extension direction of the valley portion. Then, the coordinates of the smooth line are recorded in the geological structure information storage unit 23 as a soft portion.
In FIG. 6D, a smooth line SP1 connecting low velocity regions in the extension direction of the two valleys is generated, and the position (coordinates) of the smooth line SP1 is stored in the geological structure information storage unit 23.

On the other hand, when it is determined that there is no continuous low speed region (in the case of "NO" in step S1-6), the control unit 21 of the evaluation device 20 specifies the continuous low speed region as a soft portion in the recording process. (Step S1-7) is skipped.

Then, when steps S1-4 to S1-7 are repeatedly executed for all of the divided target areas, the geological structure evaluation process is terminated.
For example, in the vertical sectional view VP1 of FIG. 7A and the horizontal sectional view HP1 of FIG. 7B, the coordinates of the broken line are specified as the soft portion and recorded in the geological structure information storage unit 23.

(Verification of the identified soft part)
When the planned excavation area in front of the tunnel face was dug at the actual site, the soft part that actually appeared in the planned excavation area and the position of the soft part shown by the broken line in FIG. 7 in the planned excavation area 31 were almost the same. It turned out to match.

According to this embodiment, the following effects can be obtained.
(1) In the present embodiment, the control unit 21 of the evaluation device 20 executes the process of specifying the extension direction of the valley portion from the low speed unit (step S1-5), and there is a continuous low speed region (step S1). In the case of “YES” in −6), the recording process is executed with the continuous low-speed region as the soft portion (step S1-7). As a result, the soft part, which was difficult to detect by the reflection method elastic wave exploration, can be accurately evaluated by using the elastic wave velocity distribution map.

(2) In the present embodiment, the control unit 21 of the evaluation device 20 executes a determination process (step S1-6) as to whether or not there is a continuous valley portion by using the continuous condition. The continuous condition includes that the deviation in the extension direction of both valleys is within an allowable range. As a result, the soft part can be accurately evaluated by using the elastic wave velocity distribution map in consideration of the continuity of the geological structure.

(3) In the present embodiment, the control unit 21 of the evaluation device 20 executes the division process for each target area (step S1-3), and determines the presence or absence of a continuous low speed region for each target area (step). S1-6). In tunnel excavation, it may be necessary to grasp the relative soft part contained in the hard geology. Therefore, even when the target area includes a region in which a relatively high speed region occupies a large proportion and a region in which a low speed region occupies a large proportion, it is possible to grasp the soft portion in each target area.

(4) In the present embodiment, the control unit 21 of the evaluation device 20 cuts out the vertical sectional view VP1 and the horizontal sectional view HP1 in the process of creating the two-dimensional velocity distribution sectional view (step S1-2), and each sectional view ( The soft part is specified in VP1 and HP1). As a result, the position of the soft portion can be grasped from two orthogonal plane directions and height directions.

(5) In the present embodiment, in the vertical sectional view VP1 and the horizontal sectional view HP1, each target area is divided so that the tunnel 30 and the planned excavation area 31 are located at the center. This makes it possible to evaluate the geological structure of the ground around the tunnel.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
In the above embodiment, in the determination process (step S1-6) of whether or not there is a continuous low speed region, the control unit 21 of the evaluation device 20 determines the distance between the ends of both valleys and the extension of the valleys. The deviation of the direction was used. Here, the process of determining whether or not there is a continuous low-speed region is not limited to the process performed by using the distance between the ends of both valleys and the deviation in the extension direction of the valleys. For example, depending on the nature of the geology in which the valley exists, the extending direction of the geology may be specified, and this direction may be used to execute a determination process of whether or not there is a continuous low velocity region.

For example, as shown in FIG. 8, it is assumed that a chert area exists as geology in the planned excavation area. In this chert region, multiple geological layers are often deposited in layers. Therefore, even if the end of the valley in the chart region is separated from the other ends, the extending direction of the soft portion already identified in this chart region and the direction in which both valleys are continuous are substantially the same. If they are parallel, it may be determined that the low speed regions including both valleys are continuous.

When the low speed region extends in the direction of the broken line shown in the chart area shown in FIG. 8, two two within the allowable range angle in the direction of the low speed region (almost parallel to the direction of the low speed region). The broken line arrow determines that the low speed region is continuous even if the distance is long.

In addition, when the geology including the low-velocity part has an annular continuity (extending direction) or a radial continuity, it is based on the extending direction of other low-speed parts and the interval of the velocity contour. , It can be determined that the low speed region including the valley is continuous. Furthermore, in the case of granite geology, since there are many square joints, the extension direction when two separated valleys are connected is a predetermined angle range orthogonal to the extension direction of the other valleys. In the case of, it can be determined that the low speed region including the valley portion is continuous.

-In the above embodiment, the control unit 21 of the evaluation device 20 executes the process of specifying the extension direction of the valley portion from the low speed portion. Here, as a low-velocity part, a closed figure in which the velocity of the elastic wave is the minimum value is specified. The method of specifying the extension direction of the valley is not limited to this. For example, the contour interval and shape may be specified based on the curvature of the minimum velocity portion and the constant velocity region (minimum curvature portion), and the extension direction of the valley portion may be specified. Further, if the extension direction of the valley can be specified, the contour interval and shape are not limited to the case of specifying based on the curvature of the constant velocity region, and the amount of change in the contour curve (calculated value by differentiation, etc.) can be determined. It may be specified by using.

In the above embodiment, in the process of specifying the extension direction from the low speed portion to the valley portion (step S1-5), the control unit 21 of the evaluation device 20 repeatedly identifies the protruding portion and connects the specified protruding portion. Identify the extension direction of the valley. Here, when the extension directions of a large number of valleys can be specified from the low speed portion LS1, the valleys may be limited to the main extension directions. Here, as the main extension direction, for example, an extension direction of a valley portion having a wide interval of lower speed contours, a direction substantially parallel to the extension direction of other low speed portions, or the like can be used. Then, the determination process of whether or not there is a continuous low speed region may be executed depending on whether or not there is an end of another valley portion that satisfies the continuous condition at the end portion in the extension direction. As a result, even if there are many valleys, the soft part can be quickly identified.

-In the above embodiment, the target area is divided in the portion where the speed change is gradual. The division of the target area for evaluation is not limited to this. For example, the target area may be divided by a predetermined distance. Further, the cross-sectional view may not be divided into one target area, and it may be determined whether or not there is a continuous low-speed portion using constant velocity. Further, the target area may be divided so that a part of the target area overlaps. In this case, the geological structure can be evaluated by dividing into an arbitrary target area including a part of the soft part and the periphery of the soft part.

-In the above embodiment, a horizontal sectional view and a vertical sectional view are cut out in the three-dimensional elastic wave velocity distribution map. The two-dimensional cross-sectional views cut out in the three-dimensional elastic wave velocity distribution map are not limited to these cross-sectional views. For example, if there is a plane with an angle that is easy to grasp other than a horizontal plane or a vertical plane in the ground, a cross-sectional view on that plane may be used, or three or more cross-sectional views may be cut out and used. May be good.
Further, in the above embodiment, the horizontal cross-sectional view and the vertical cross-sectional view are cross-sectional views in which the central axis thereof is the central axis of the tunnel and the front of the tunnel face. The cross-sectional position is not limited as long as it is a cross-sectional view including the tunnel and the front of the tunnel face. For example, the front of the tunnel and the tunnel face may be shifted upward or sideways, and the cross-sectional view may be centered on an axis parallel to the central axis of the tunnel and the front of the tunnel face. In this case, the geological structure in any direction, not limited to the tunnel and the front of the tunnel face, can be grasped in more detail.

-In the above embodiment, the geological structure of the ground was evaluated using an elastic wave velocity distribution map including the position (coordinates) of the reflecting surface in front of the tunnel face. The elastic wave velocity distribution map to be evaluated is not limited to this. For example, the geological structure of the ground may be evaluated using a three-dimensional velocity distribution map that does not include a reflecting surface. Further, the geological structure may be evaluated by using the position of the reflecting surface included in the three-dimensional velocity distribution map. For example, the reflective surface includes a soft to hard (low to high speed) reflective surface and a hard to soft (high to low speed) reflective surface. Therefore, when the ends of the plurality of valleys are separated from each other in the region determined to be the soft portion before and after the reflective surface, they may be specified as a continuous soft portion.

-In the above embodiment, when the control unit 21 of the evaluation device 20 determines that there are continuous low-speed regions, these low-speed regions are continuously specified to specify the position of the soft portion. The position of the soft portion is not limited to the case where the control unit 21 of the evaluation device 20 specifies it, and a person may determine it by using the two-dimensional velocity distribution cross-sectional view. In this case, the control unit 21 of the evaluation device 20 may output a two-dimensional cross-sectional view from the three-dimensional elastic wave velocity distribution map, or output a two-dimensional cross-sectional view including the extension direction of the valley portion. May be good. Then, the geological structure of the ground may be evaluated using the output two-dimensional cross-sectional view.

A1 ... region, HP1 ... horizontal sectional view, H10 ... information processing device, H11 ... communication device, H14 ... storage unit, H15 ... processor, LS1 ... low speed unit, RS1 ... reflective surface, VP1 ... vertical sectional view, 10 ... measurement Device, 15 ... Input device, 16 ... Display device, 20 ... Evaluation device, 21 ... Control unit, 23 ... Geological structure information storage unit, 30 ... Tunnel, 30f ... Face surface, 31 ... Expected excavation area, 212 ... Area identification unit , 213 ... Soft part specific part.

Claims (6)

This is a geological structure evaluation method that evaluates the geological structure using an elastic wave velocity distribution map.
Identify the low velocity part in the elastic wave velocity distribution map in the target area,
The extension direction of the valley portion extending from the low speed portion is specified by using the interval and shape of the velocity contour around the low speed portion.
A geological structure evaluation method characterized in that when it is determined that a plurality of low velocity regions are continuous by using the extension direction of the valley portion, it is specified as a soft portion in the target area. The elastic wave velocity distribution map is a three-dimensional distribution of elastic wave velocities.
From the elastic wave velocity distribution map, a two-dimensional cross-sectional view including the planned excavation area of the tunnel is generated.
Based on the number of contours in the two-dimensional cross-sectional view, it is divided into a plurality of target areas.
The geological structure evaluation method according to claim 1, wherein a low-speed portion is specified for each of the divided target areas, and a determination process for determining whether or not a plurality of low-speed regions are continuous is executed. At the end of the valley, when the ends of the other valleys are close to each other within a predetermined distance and the deviation of the valley in the extension direction is within the allowable range, the valley and the other valley The geological structure evaluation method according to claim 1 or 2, wherein a position in which the above is continuous is specified as the soft portion. When the extension direction that connects the valley portion and the other valley portion is located in the extension direction of the geology specified according to the nature of the geology including the valley portion, the valley portion and the other valley portion are located. The geological structure evaluation method according to any one of claims 1 to 3, wherein the position where the portions are continuous is specified as the soft portion. It is a geological structure evaluation system that evaluates the geological structure with a control unit connected to the elastic wave velocity distribution map storage unit that stores the elastic wave velocity distribution map.
The control unit
Identify the low velocity part in the elastic wave velocity distribution map in the target area,
The extension direction of the valley portion extending from the low speed portion is specified by using the interval and shape of the velocity contour around the low speed portion.
A geological structure evaluation system characterized in that when it is determined that a plurality of low velocity regions are continuous by using the extension direction of the valley portion, it is specified as a soft portion in the target area. This is a program that evaluates the geological structure using a geological structure evaluation system equipped with a control unit connected to the elastic wave velocity distribution map storage unit that stores the elastic wave velocity distribution map.
The control unit
Identify the low velocity part in the elastic wave velocity distribution map in the target area,
The extension direction of the valley portion extending from the low speed portion is specified by using the interval and shape of the velocity contour around the low speed portion.
A geological structure evaluation program characterized by functioning as a means for identifying a soft portion in the target area when it is determined that a plurality of low velocity regions are continuous using the extension direction of the valley portion. ..

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